If you got that message, and your internet connection works, it means you have a firewall software that is blocking online access to the installer, so you have to properly configure it to allow online access to the installer, or just turn it off.
In any case, if you download the latest Addon Manager, every single file included in the installer is exactly the same as the files that are online now, so it will surely work even without an internet connection. Never, ever, install something older over something new, it will most likely never work.
CYVR works only with the most current version of the Addon Manager, which is included in its Full 1.1 installer OR in the latest Stand-Alone Addon Manager installer.